[Yamamoto, Ushiba]

Abstract:
ETMY photosensors' spectra were checked again after ADC noise investigation.
Then, we found many strange peak stractures and large excess of several photosensors, which are obtained in previous spectra measurement, are coming from ADC.
Though MNH1 and IMV3 photosensors seem to have slightly larger noise, they look acceptable.

Detail:
After ADC noise investigation (klog20682), we checked photosensor noise by using relatively better noise performance channels of ADC (ADC1 channel 3-7).
Figure 1 shows the result.
Black line is the ADC noise level of each channel, and other lines are photosensor noise (see legend for confirming which photosensor noises are shown).

Figure 2 shows the photosensor noises at MN stage (top) and IM stage (bottom).
Followings are some remarkable notes:
1. MNH1 photosensor has slightly larger noise than the other MN photosensors between 2Hz and 40Hz.
2. IMV3 photosensor has larger noise than the other IM photosensors between 0.8Hz and 100 Hz.
3. Below 0.1Hz, almost all photsensor noises are limited by AC noise.

For 1, it doesn't seem a big problem because the excess noise is very small (less than a factor of 2).
For 2, it also doesn't a big problem because IM photosensor won't be used for local control.
Tomorrow, I will continue to investigate where these noise differences are coming but no large hardware trouble was not found.

Note:
Measured data was stored at /users/VISsvn/TypeApayload/ETMY/Spectra/20220510/.